How hard can this be?

I have two subreports on my main report. They are supposed to be linked on a StaffId field. There are two tables, Staff and Tasks, both with a StaffId field. The main report is grouped by StaffId and the subreports are in the group footer for StaffId. I set up the links as instructed on the StaffId field. First of all I got no filtering whatsoever in the subreports. I then discovered that if I added a group selection formula, I got the filtering I wanted, with one major problem: the summary at the bottom of the subreport continues to summarise data from all records, not just the displayed, filtered records. This is starting to give me apoplexy. I would assume that if the record selection formula for the subreport filters the data on the StaffId, then everything, including summary fields, should be done on the selected records. Oh for a good old Access report, where everything works according to logic!